The background on which the present invention has been devised will first be described. In the field of consumer products and communication equipment, much effort has been paid positively to enhance the degree of miniaturization and preciseness. Especially, quartz crystal resonators used in such devices must be miniaturized, and quartz crystal units of a surface mounting type are required to generate frequencies of 1.5 MHz to 4.2 MHz. The present invention has been devised in view of the foregoing circumstances. That is, the quartz crystal resonator of the present invention is one usable as a reference signal source of various devices, such as consumer products and communication equipment; or, the present invention relates to a face shear mode quartz crystal resonator adapted to fabricate the surface mounting type which has a vibrational portion and supporting portions formed by an etching method.
The conventional face shear mode quartz crystal resonator is shaped by machining and generally it is supported by two thin lead wires attached to the center of a square plate. Therefore, the conventional resonator is difficult to minaturize and weak with respect to shock and exhibits a large energy loss caused by vibration at supporting points; accordingly, no face shear mode quartz crystal resonator could be fabricated that has a small motional series resistance R.sub.1 and a large quality factor. Further, in view of the foregoing method of support, the conventional face shear mode quartz crystal resonator fabricated through machining is limited in terms of miniaturization when produced in large quantity, and with the realizable size of the resonator, the frequency is limited to 500KHz at best, or frequencies higher than the above can hardly be attained. On the other hand, the process of incorporating the vibrational portion and supporting portions in the quartz crystal resonator using the etching method adopted in the present invention is adopted also in Japanese Patent Publication Nos. 58-47883 and 61-44408, Japanese Patent Laid-Open No. 53-132988, U.S. Pat. Nos. 4,350,918, 4,447,753, 4,484,382 and 4,633,124, etc., these disclosing GT cut quartz crystal resonators involving two width-extensional and length-extensional modes. This process is known as being adapted for use as the method of fabricating a quartz crystal resonator. Therefore, the present invention has applied the etching method well known in the art to the face shear mode quartz crystal resonator of the present invention to overcome the foregoing defects. Although the shape of the face shear mode quartz crystal resonator of the present invention is analogous to those of the resonators disclosed in the above-mentioned patents, the vibration mode of the resonator of the present invention differs intrinsically from those of the prior patents, and the way of thinking to determine the shape and size of the resonator differs basically from that of the prior art.